Quote:
Originally Posted by originaltrilogy
Most threads I read have users refocus for each colours anyway to get best results even for parfocal filters, I thought if refocus anyway maybe achro would do as good.
So people use mono camera and achro for sun or moon should probably use APO instead for mono work?
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I think it's fair to say that most achros are low-end instruments and have generally poor focussers, I know mine does. You'll end up paying almost as much for a completely square and repeatable focusser as you would for an ED scope anyway. The ED would also give you the flexibility of shooting in colour if you wanted. Can't comment more than that as I've never shot anything planetary other than the moon.